Testing means the process by which the hazards that may confront entrants of a permit
space are identified and evaluated. Testing includes specifying the tests that are to be
performed in the permit space. If electronic or thermal equipment is used to perform
such tests, and the possibility exists of an explosive substance or a hazardous atmosphere
due to flammable gases and vapors, then the testing equipment must be approved for use in
such explosive or flammable conditions as required by section 2540.2.

(3) The air shall be tested with an appropriate device or method to determine whether
dangerous air contamination and/or oxygen deficiency exists.and aA
written record of such testing results shall be made and kept at the work site for the
duration of the work. Affected employees and/or their representative shall be afforded an
opportunity to review and record the testing results. If an electronic or thermal
device is used to test a confined space that contains or is likely to develop a dangerous
air contamination due to flammable and/or explosive substances, then the device must be
approved for use in such explosive or flammable conditions as required by section 2540.2.

* * *

(e) Confined Space Operations.

(1) Entry Into and Work Within Confined Spaces.

* * *

(F) Work involving the use of flame, arc, spark, or other source of ignition is
prohibited within a confined space (or any adjacent space having common walls, floor, or
ceiling with the confined space) which contains, or is likely to develop, dangerous air
contamination due to flammable and/or explosive substances.

(c) No source of ignition shall be permitted in any location, indoors or outdoors,
where the concentration of the flammable gases or vapors exceeds or may reasonably be
expected to exceed 25 percent of the lower explosive limit. Tests shall be made to
ascertain that this limit is not exceeded before a source of ignition is introduced into
such location, and such tests shall be repeated frequently (or a continuous indicator
used) as long as conditions giving rise to such concentrations of flammable vapors or
gases continue and a source of ignition is present. If electronic or thermal testing
equipment is used, it must be approved for use in such flammable conditions as required by
section 2540.2.

(e) Precautions and Order of Testing Before Entering Confined and Enclosed Spaces and
Other Dangerous Atmospheres. The employer shall ensure that atmospheric testing is
performed in the following sequence: oxygen content, flammability, toxicity. If
electronic or thermal equipment is used for testing and the possibility exists of an
explosive substance or a flammable atmosphere, then the testing equipment must be approved
for use in such explosive or flammable conditions as required by section 2540.2.